Priority is claimed to Patent Application No. 00-72596 filed in the Republic of Korea on Dec. 1, 2000, herein incorporated by reference.
1. Field of the Invention
The present invention relates to an apparatus for recording and reading data and a method for recording and reading data thereof, and more particularly, to an apparatus for recording and reading data by measuring output voltage variations introduced by contact resistance between a data storage medium and a probe tip.
2. Description of the Related Art
With developments in the scanning probe microscope, it is possible to observe new physical phenomena in terms of various atomic levels. In addition, research on data storage based on the findings observed by scanning probe microscopes has become more active. Until now, in particular, a variety of research efforts into developing data storage media and recording/reading data have been carried out. Mostly, the purpose of such research has been to realize data storage media capable of recording and reading data bits on the order of several nanometers or even to the atomic level with the use of magnetic material, piezo-electric material or charge traps and taking advantage of phase transformation. However, in a case where data storage media are formed of piezo-electric material or charge traps, the media may cause a critical problem with data retention and signals stored in the media are very weak. Thus, in this case, it is necessary to develop a highly sensitive sensing probe capable of reading such data bits of atomic size or on the order of several nanometers.
International Business Machines Corp. has developed a data storage medium formed of polymer. However, this type of medium also has limits in sensitivity and the data read speed, which will be described with reference to FIGS. 1A through 2B.
FIGS. 1A and 1B illustrate the data recording and reading mechanisms of an apparatus for recording and reading data using a conventional polymer medium. Referring to FIG. 1, a tip 11 is heated by current I applied through a cantilever 12 and then, polymer 13 which is a medium is melted by the tip 11, so that a unit of data (e.g., a bit) 15 can be written on the polymer 13. As the polymer 13 becomes thinner, it is possible to write a bit 15 having a smaller size on the polymer 13.
Referring to FIG. 1B, in the case of sensing the polymer 13 with the tip 11 to read data, the tip 11 is also heated by current applied through the cantilever 12 and the heated tip 11 scans the surface of the polymer 13. Here, the temperature of the tip 11 is maintained to such an extent that the polymer 13 does not melt. There is a difference in heat conductivity between scanning the surface of the polymer 13 with the probe and scanning the bottom surface of the bit 15 with the probe. Accordingly, the amount of current flowing at one side of the probe is different from the amount of current flowing at the other side of the probe. Then, the probe reads data by sensing the difference in temperature. In other words, the probe detects a difference in temperature in the case of sensing the polymer 13 and the bit 15. If the bit 15 recorded on the polymer 13 has a greater depth, it is possible to obtain a higher signal-to-noise ratio in reproducing data. As described above, in order to record bits having a smaller size on the polymer 13, the polymer 13 must be formed to be thinner. However, if the polymer 13 is too thin, problems with sensing sensitivity and signal-to-noise ratio may arise. According to the prior art, it is preferable that the thickness of the polymer 13 on the substrate 14 is about 40 nm, however, in a case where polymer 13 having such a thickness is used, an amplification circuit is needed to read weak signals comprised of finely sized bits.
Meanwhile, as it is possible to highly densify data to be recorded in an apparatus for recording and reading data, the amount of data recordable in an apparatus for recording and reading data increases. As a result, it becomes necessary for an apparatus for recording and reading data to read the data at high speeds. The data read speed is related to the natural oscillation frequency of a probe. In a case where a probe reads data by sensing differences in temperature as in the prior art, a thermal time constant may also have an influence on the data read speed. However, in this case, as shown in FIGS. 2A and 2B, it is difficult to obtain clean images. FIG. 2A is a scanning electron micrograph (SEM) image showing bits on a conventional data storage medium and FIG. 2B is a SEM image showing data read by a conventional apparatus for recording and reading data.
Therefore, to solve these problems with the prior art concerning small-sized bits, the data read speed and the signal-to-noise ratio, it is necessary to develop a new apparatus for recording and reading data and a method for recording and reading data thereof.
To solve the above problems, it is an object of the present invention to provide an apparatus for recording and reading data which is capable of reducing the size of a data unit (or at least width of data units in the case of run-length encoding and the like), enhancing the data read speed, and obtaining a high signal-to-noise ratio and a method for recording and reading data thereof.
Accordingly, to achieve the above object, there is provided an apparatus for recording and reading data comprising: a storage medium on which data is recorded; and a probe which is installed to face the storage medium and is used for recording data on the storage medium and reading the data recorded on the storage medium, wherein the storage medium comprises a substrate; a conductive layer which is formed on the substrate; and a dielectric layer which is formed on the conductive layer wherein said system further comprises a circuit for reading the data, connected between said probe and said conductive layers that determines an output voltage value that varies depending on a portion of said storage medium being scanned by said probe.
Preferably, holes are formed on predetermined portions of the dielectric layer so as to expose the top surface of the conductive layer. Preferably, the dielectric layer is formed of one among the group consisting of an organic material, a polymer, a wax and a liquid crystal, and the conductive layer is formed of one among the group consisting of metal and semiconductor.
Preferably, the substrate is one of a silicon substrate, a glass substrate, and a metal substrate.
The probe comprises a cantilever and a tip fixed on the cantilever. Preferably, the cantilever is formed of one of Si, SiN and dielectric material, the tip is formed of silicon and the surface of the tip is coated with a metal layer.
The probe operates a predetermined distance apart from the storage medium or in contact with the storage medium. The probe further comprises a first contact pad and a second contact pad which are connected to short lines of the cantilever, the short line connected to the first contact pad is in contact with the probe tip and the short line connected to the second contact pad is not in contact with the probe tip.
To achieve the above object, there is provided a method for recording and reading data in an apparatus for recording and reading data comprising a storage medium which comprises a substrate, a conductive layer formed on the substrate and a dielectric layer formed on the conductive layer; and a probe which is installed to face the storage medium and is used for recording data on the storage medium and reading the data recorded on the storage medium, comprising: recording data by forming a hole on a predetermined portion of the dielectric layer to expose the surface of the conductive layer; and reading data by scanning the surface of the storage medium with the probe and sensing the variation of output voltage value caused by contact between the probe and the storage medium storage medium.
The probe comprises a cantilever and a tip fixed on the cantilever. The hole is formed by applying current to the probe to heat the tip and melting the dielectric layer with the heated tip.
Variations in output voltage are caused by a short circuit between the tip and the surface of the conductive layer exposed by the hole in scanning the dielectric layer with the tip and is measured by a voltmeter included in the apparatus for recording and reading data.
To achieve the above object, there is provided a method for recording and reading data in an apparatus for recording and reading data comprising a storage medium which comprises a substrate and a conductive layer formed on the substrate; and a probe which is installed to face the storage medium and is used for recording data on the storage medium and reading the data recorded on the storage medium, comprising: recording data by forming a hole on a predetermined portion of the conductive layer to expose the surface of the conductive layer; and reading data by scanning the surface of the storage medium with the probe and sensing variations in the output value caused by contact between the probe and the storage medium.
The hole is formed by applying current to the probe to heat the tip and melting the dielectric layer with the heated tip. If the tip encounters the hole during scanning of the conductive layer, at which the tip and the conductive layer are shorted by each other, output voltage is reduced to 0 V around the hole and variations in output voltage is measured by a voltmeter included in the apparatus for recording and reading data.